Successful Use of a New Guidewire with Radiofrequency Ablation Capability for the Treatment of Chronic Total Occlusion at the Os

The major limitation of percutaneous therapy (PCI) for the treatment of chronic total occlusions (CTOs) is the inability to cross with a wire. We report successful recanalization of a CTO situated at the ostium of the left anterior descending artery. The lesion demonstrated several anatomical features known to be associated with an unsuccessful outcome, and attempts with conventional wires failed. However, recanalization was facilitated with the Intraluminal Wire,™ (Intraluminal Therapeutics, Inc., Carlsbad, California) a novel technology that combines guidance of the wire tip with the capability of radiofrequency ablation. The majority of patients with CTOs are currently managed medically or referred for coronary bypass surgery. However, drug-eluting stent (DES) implantation for the treatment of CTOs has been shown to reduce the subsequent rate of restenosis compared with bare metal stents. If rates of successful recanalization can be increased with new technologies such as demonstrated here, then the advent of DESs will lead to more widespread applicability of PCI for this complex group. Case report. A 58-year-old woman was referred with a 2-year history of chest pain. Risk factors for coronary disease were smoking, hypertension, and a positive family history. Though the resting ECG was normal, an exercise test demonstrated ST-depression across the anterior leads during stage 2 of a Bruce protocol. Subsequent coronary angiography showed single-vessel disease of the left anterior descending artery (LAD) which was completely occluded at the ostium, with a blunt stump (Figure 1). Notably, there was clearly identified heavy calcification, and a ring of calcium can be seen in Figure 1B (arrow). There was some antegrade filling via small bridging collaterals originating from the proximal part of the left circumflex artery (Figure 1A). The distal vessel was also filled via retrograde collaterals from the right coronary artery (Figure 1B). Left ventricular function was normal, with no anterior wall movement abnormality. The patient was taking long-term aspirin, and before the procedure, was pre-loaded with 300 mg clopidogrel. Heparin was administered to maintain the activated clotting time > 250 seconds. A 7 Fr left Amplatz 2 guiding catheter was used to catheterize the left main coronary artery, and the procedure was carried out utilising biplane X-ray screening. By quantitative coronary angiography, the estimated length of the occlusion was 13.6 mm. Initial attempts to open the LAD were made using an Intermediate tip 0.014 inch guidewire (Boston Scientific, Maple Grove, Minnesota), and then a 0.014 inch Miracle 3 g wire (Asahi Intecc Co. Ltd, Japan) with over-the-wire balloon support. However, both these wires prolapsed into the circumflex artery with no antegrade progress into the LAD (Figure 2B). The Intraluminal wire was then advanced to the stump and radiofrequency ablation applied, which was able to penetrate the proximal cap of the occlusion (Figure 2C). The Intraluminal wire was substituted for the Miracle wire (Asahi Intecc Co. Ltd., Aichi, Japan), with successful wire passage into the distal vessel lumen (figure 2D). Following pre-dilatation, a 3.0 x 18 mm sirolimus-eluting stent (CYPHER™ drug-eluting stent, Cordis Corporation, Miami, Florida) was implanted (Figure 2E) and subsequently post-dilated with a 3.5 mm balloon; the final result was excellent (Figure 2F). At 6-month follow-up, the patient was symptom-free and underwent a repeat exercise test. On this occasion she managed 10 minutes of a Bruce protocol (maximum predicted heart rate attained) without chest discomfort or ECG changes. Discussion. Previous studies have demonstrated the importance of CTO revascularization, with improvement in anginal symptoms, exercise capacity, and left ventricular function.^1–3 In addition, successful recanalization reduces the need for subsequent coronary artery bypass surgery,⁴ and long-term evaluation has shown a 10-year survival advantage of 73.5% compared to 65.1% in patients in whom PCI is unsuccessful.⁵ The Safecross system with the Intraluminal Guidewire™ (Intraluminal Therapeutics, Carlsbad, California) uses optical coherence reflectometry to determine the position of the wire tip. The system has been previously described.^6–9 Briefly, a beam of near-infra red light is emitted and the reflected beam analyzed to differentiate the vessel lumen from the outside vessel wall. The technology therefore provides information for guidance of the wire to reduce the risk of taking an extra-luminal passage potentially leading to perforation and pericardial tamponade. In addition, the wire has the capability of radiofrequency ablation at the tip, emitting short bursts (100 ms) of low frequency 250–500 kHz energy. This facilitates forward passage of the wire with efficacy demonstrable even in calcified vessels.⁷ The system combines these two capabilities such that ablation is only enabled when the wire tip is heading correctly. In the present case, the Intraluminal was of great value in penetration of the proximal cap of the occlusion which, particularly when the stump appears blunt, can be composed of very dense fibrotic material. The cap was unable to be breached by conventional wires, yet once a few millimeters of antegrade passage had been made with the Intraluminal wire, the remainder of the occlusion could be traversed. Importantly, the distal LAD was filled via collaterals, thereby facilitating wire guidance and enabling reassurance of successful recanalization with visualization of the wire within the distal lumen. However, the Intraluminal system uses optical coherence reflectometry to determine the position of the distal tip of the wire in relation to the vessel wall. This does not therefore rely on angiographic visualization, and with more experience in the future, it may be possible to use the system even when the distal vessel is not well visualized. When treating CTOs, whatever the technology used, the principles of good backup support remain important, and in this case a left Amplatz guide catheter proved effective. In addition, to facilitate the exchange of wires and to provide additional backup, we routinely utilize a 1.5 mm over-the-wire balloon, which can then be used for pre-dilatation once the occlusion has been successfully crossed with a wire. Certain lesion characteristics have been shown to affect the success rate of recanalization. Some of the most important adverse features include increased age and length of the occlusion, the presence of bridging collaterals, a side branch at the site of occlusion, calcification, and an abrupt, rather than tapered stump.¹⁰ Our patient’s clinical history suggested that the occlusion was two years old, was ostial in location with the large circumflex artery originating at the occlusion, was heavily calcified, and the stump was abrupt (Figures 1 and 2). All these features suggested that the chances of successful recanalization would be low, and might have led many cardiologists to refer similar patients directly for bypass surgery. Indeed, in the BARI study, clinicians provided their views on the suitability of lesions for a revascularization strategy of PCI versus CABG, and both ostial lesion location and a CTO were deemed to be strong non-favorable characteristics for PCI.¹¹ Percutaneous treatment of ostial LAD lesions could potentially jeopardize the circumflex artery, however in the present case, the use of biplane imaging facilitated precise stent positioning which, together with a relatively large angle of the left main stem carina, meant that the final result was excellent. Long-term results of PCI with bare metal stents have been hindered by the development of restenosis, with rates of non-occlusive ostial LAD lesions as high as 26%.¹² Furthermore, CTOs are well-known to be at increased risk of restenosis, with rates of 32–55%.^13–16 However, recent data have confirmed the efficacy of sirolimus-eluting stents for CTOs, with a rate of 96% for 1-year survival-free of major adverse events, and a binary restenosis rate of 9%.¹⁷Conclusions. This case demonstrates the potential of this novel technology, particularly at successfully penetrating the proximal cap of a CTO following failed attempts using conventional guidewires. Future improvements in such specialized technologies will improve the ability to achieve successful recanalization of CTOs. This, together with the use of drug-eluting stents, means that the use of PCI, rather than CABG, will be more widely applicable for the revascularization of patients with complex CTOs.

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